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authorDavid S. Miller <davem@davemloft.net>2010-05-18 23:01:55 -0700
committerDavid S. Miller <davem@davemloft.net>2010-05-18 23:01:55 -0700
commit2ec8c6bb5d8f3a62a79f463525054bae1e3d4487 (patch)
treefa7f8400ac685fb52e96f64997c7c682fc2aa021 /Documentation/trace/ftrace.txt
parent7b39f90fabcf9e2af0cd79d0a60440d821e22b56 (diff)
parent537b60d17894b7c19a6060feae40299d7109d6e7 (diff)
Merge branch 'master' of /home/davem/src/GIT/linux-2.6/
Conflicts: include/linux/mod_devicetable.h scripts/mod/file2alias.c
Diffstat (limited to 'Documentation/trace/ftrace.txt')
-rw-r--r--Documentation/trace/ftrace.txt50
1 files changed, 48 insertions, 2 deletions
diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 03485bfbd79..557c1edecca 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -155,6 +155,9 @@ of ftrace. Here is a list of some of the key files:
to be traced. Echoing names of functions into this file
will limit the trace to only those functions.
+ This interface also allows for commands to be used. See the
+ "Filter commands" section for more details.
+
set_ftrace_notrace:
This has an effect opposite to that of
@@ -1337,12 +1340,14 @@ ftrace_dump_on_oops must be set. To set ftrace_dump_on_oops, one
can either use the sysctl function or set it via the proc system
interface.
- sysctl kernel.ftrace_dump_on_oops=1
+ sysctl kernel.ftrace_dump_on_oops=n
or
- echo 1 > /proc/sys/kernel/ftrace_dump_on_oops
+ echo n > /proc/sys/kernel/ftrace_dump_on_oops
+If n = 1, ftrace will dump buffers of all CPUs, if n = 2 ftrace will
+only dump the buffer of the CPU that triggered the oops.
Here's an example of such a dump after a null pointer
dereference in a kernel module:
@@ -1822,6 +1827,47 @@ this special filter via:
echo > set_graph_function
+Filter commands
+---------------
+
+A few commands are supported by the set_ftrace_filter interface.
+Trace commands have the following format:
+
+<function>:<command>:<parameter>
+
+The following commands are supported:
+
+- mod
+ This command enables function filtering per module. The
+ parameter defines the module. For example, if only the write*
+ functions in the ext3 module are desired, run:
+
+ echo 'write*:mod:ext3' > set_ftrace_filter
+
+ This command interacts with the filter in the same way as
+ filtering based on function names. Thus, adding more functions
+ in a different module is accomplished by appending (>>) to the
+ filter file. Remove specific module functions by prepending
+ '!':
+
+ echo '!writeback*:mod:ext3' >> set_ftrace_filter
+
+- traceon/traceoff
+ These commands turn tracing on and off when the specified
+ functions are hit. The parameter determines how many times the
+ tracing system is turned on and off. If unspecified, there is
+ no limit. For example, to disable tracing when a schedule bug
+ is hit the first 5 times, run:
+
+ echo '__schedule_bug:traceoff:5' > set_ftrace_filter
+
+ These commands are cumulative whether or not they are appended
+ to set_ftrace_filter. To remove a command, prepend it by '!'
+ and drop the parameter:
+
+ echo '!__schedule_bug:traceoff' > set_ftrace_filter
+
+
trace_pipe
----------